📚 Year 10 Eduqas Economics: Key Formulas & Theorems Quick Reference Handbook | Year 10 Eduqas 经济：公式定理速查手册
This quick reference handbook brings together the essential formulas, theorems and graphical relations you need to master Year 10 Eduqas Economics. From the fundamental problem of scarcity to elasticities, cost curves and macroeconomic indicators, each section is designed for rapid revision and secure understanding. Keep it close for homework, mocks and end‑of‑topic tests.
本速查手册汇总了 Year 10 Eduqas 经济课程必须掌握的关键公式、定理与图形关系。从基础的稀缺性问题到弹性、成本曲线和宏观经济指标，每一节都旨在帮助你快速复习、巩固理解。作业、模拟考和单元测验时随时查阅。
1. Fundamental Economic Concepts & Formulas | 基本经济概念与公式
Scarcity forces every economy to make choices. Opportunity cost captures what is given up when a choice is made – it is the value of the best alternative forgone.
稀缺性迫使每个经济体做出选择。机会成本衡量了做出选择时所放弃的东西——它是放弃的次优选项的价值。
Opportunity cost = Value of next best alternative forgone
This central idea is illustrated by the production possibility frontier (PPF), which shows the maximum combinations of two goods an economy can produce with full employment of current resources and technology. The PPF is usually drawn concave to the origin, reflecting the law of increasing opportunity cost – as more of one good is produced, ever‑greater quantities of the other must be sacrificed.
这一核心理念由生产可能性边界 (PPF) 加以说明。PPF 显示了在充分利用当前资源与技术下，一个经济体能够生产的两种商品的最大产量组合。PPF 通常画成凹向原点，反映了机会成本递增定律——当一种商品产量增加时，需要牺牲的另一种商品数量越来越大。
Points inside the PPF represent unemployed resources or inefficiency; points outside are currently unattainable. Economic growth causes the entire PPF to shift outward, typically when the quantity or quality of resources improves or when technology advances.
PPF 内部的点代表资源闲置或低效率；外部点当前无法实现。当资源数量或质量提升、或技术进步时，经济增长会使整条 PPF 外移。
2. Law of Demand, Law of Supply & Market Equilibrium | 需求定律、供给定律与市场均衡
The law of demand states that, ceteris paribus, as the price of a good rises, the quantity demanded falls. This inverse relationship is underpinned by the law of diminishing marginal utility: each additional unit consumed provides less extra satisfaction, so consumers will only buy more if the price drops.
需求定律指出，在其他条件不变的情况下，商品价格上升时，需求量下降。这一反向关系由边际效用递减定律支撑：每多消费一单位商品，带来的额外满足感减少，因此消费者只会在价格下降时购买更多。
The law of supply states that, ceteris paribus, as the price of a good rises, the quantity supplied increases. Higher prices give producers a profit incentive to expand output, and rising marginal costs mean they need a higher price to cover the cost of extra units.
供给定律指出，在其他条件不变的情况下，商品价格上升时，供给量增加。更高的价格提供了利润激励，促使生产者扩大产量；同时边际成本递增意味着他们需要更高的价格来覆盖额外单位的成本。
Market equilibrium occurs where the demand and supply curves intersect. At this equilibrium price (Pe), the quantity demanded equals the quantity supplied. If the market price is above equilibrium, a surplus emerges and price tends to fall; if it is below equilibrium, a shortage emerges and price tends to rise. This self‑correcting mechanism is often called the invisible hand of the price system.
市场均衡出现在需求曲线与供给曲线的交点。在均衡价格 (Pe) 下，需求量等于供给量。若市价高于均衡，出现过剩，价格趋于下跌；若市价低于均衡，出现短缺，价格趋于上升。这种自我修正机制常被称为价格体系的“看不见的手”。
3. Price Elasticity of Demand (PED) | 需求价格弹性
Price elasticity of demand measures the responsiveness of quantity demanded to a change in the good’s own price. It is always negative, but economists usually work with its absolute value.
需求价格弹性衡量需求量对商品自身价格变化的反应程度。其值恒为负，但经济学家通常使用绝对值。
PED = %Δ Quantity demanded ÷ %Δ Price
ge than price. Unitary elastic demand occurs when PED = 1. When PED > 1, demand is elastic – to price changes. At the extreme, perfectly elastic demand has PED → ∞ (horizontal curve).
当 PED = 0 时，需求完全无弹性（需求曲线垂直）。当 0 < PED < 1 时，需求缺乏弹性，即数量的变动百分比小于价格变动百分比。PED = 1 时为单位弹性。PED > 1 时需求富有弹性，消费者对价格变化非常敏感。极端情况下，完全弹性需求 PED → ∞（需求曲线水平）。
and is elastic, cutting the price raises total revenue because the gain from extra units sold outweighs the lower price per unit. If demand is inelastic, raising the price raises total revenue because the fall in quantity sold is proportionally smaller.
一条重要定理将 PED 与总收入 (TR = 价格 × 数量) 联系起来。若需求富有弹性，降价会使总收入增加，因为多卖出的数量带来的收益超过了单价下降的损失。若需求缺乏弹性，提价会使总收入增加，因为销售量的减少比例较小。
Key factors affecting PED include: availability of close substitutes, whether the good is a necessity or a luxury, the proportion of income spent on the good, and the time period under consideration. Goods with many substitutes or luxuries tend to have more elastic demand.
影响 PED 的关键因素包括：近似替代品的可得性、商品是必需品还是奢侈品、支出占收入的比例以及所考虑的时间范围。替代品多或奢侈品的需求往往更富有弹性。
4. Income Elasticity of Demand (YED) and Cross Elasticity of Demand (XED) | 需求收入弹性与交叉弹性
Income elasticity of demand measures how quantity demanded changes in response to a change in consumers’ income.
需求收入弹性衡量需求量对消费者收入变化的反应程度。
YED = %Δ Quantity demanded ÷ %Δ Income
Normal goods have a positive YED. Within normal goods, necessities lie between 0 and 1, while luxuries are greater than 1. Inferior goods have a negative YED – as incomes rise, demand falls because consumers switch to superior alternatives.
正常品的 YED 为正。其中必需品 YED 在 0 到 1 之间，奢侈品 YED 大于 1。劣等品的 YED 为负——收入上升时需求下降，因为消费者转向更优选择。
Cross elasticity of demand measures the responsiveness of demand for one good to a change in the price of another good.
需求交叉弹性衡量一种商品的需求量对另一种商品价格变化的反应程度。
XED = %Δ Quantity demanded of good X ÷ %Δ Price of good Y
Substitutes have a positive XED: if the price of coffee rises, demand for tea increases. Complements have a negative XED: if the price of printers rises, demand for printer ink falls. Unrelated goods have an XED close to zero. Understanding these relationships helps firms anticipate the impact of rivals’ pricing and changes in consumer income on their sales.
替代品的 XED 为正：咖啡价格上涨，茶叶需求增加。互补品的 XED 为负：打印机价格上涨，墨盒需求下降。无关商品的 XED 接近零。理解这些关系有助于企业预估竞争对手定价和消费者收入变化对自身销售的影响。
5. Price Elasticity of Supply (PES) | 供给价格弹性
Price elasticity of supply measures the responsiveness of quantity supplied to a change in price.
供给价格弹性衡量供给量对价格变化的反应程度。
PES = %Δ Quantity supplied ÷ %Δ Price
tput quickly. Unitary elastic supply (PES = 1) and elastic supply (PES > 1) mean producers can increase output relatively easily. Perfectly elastic supply (PES → ∞) occurs when a tiny price change leads to an unlimited change in quantity supplied – rare in real markets.
PES = 0 时供给完全无弹性（如今晚音乐会的固定座位）。0 < PES < 1 时供给缺乏弹性，企业难以快速扩大产量。单位弹性 (PES = 1) 和富有弹性 (PES > 1) 意味着生产者可以相对容易地增加产量。完全弹性 (PES → ∞) 极少见，指微小价格变动导致供给量无限变化。
Determinants of PES include the time period (supply is more elastic in the long run), availability of spare capacity, ability to store stock, and the flexibility of the production process. Agricultural products often have inelastic supply in the short run because planting cycles cannot be altered quickly.
决定 PES 的因素包括时间周期（长期内供给更富有弹性）、闲置产能的可得性、库存能力以及生产过程的灵活性。农产品在短期内往往缺乏弹性，因为种植周期无法迅速改变。
6. Costs, Revenue & Profit Formulas | 成本、收益与利润公式
A firm’s cost structure is central to its production decisions. The following identities are used throughout Year 10 analysis.
企业的成本结构是其生产决策的核心。以下恒等式贯穿 Year 10 的分析。
Total Cost (TC) = Total Fixed Cost (TFC) + Total Variable Cost (TVC)
Fixed costs do not vary with output in the short run (e.g. rent, salaries of permanent staff), while variable costs change with output (e.g. raw materials, piece‑rate labour).
固定成本在短期内不随产量变动（如租金、固定员工工资），而可变成本随产量变化（如原材料、计件工资）。
Average Total Cost (ATC) = TC ÷ Quantity (Q)
Average Fixed Cost (AFC) = TFC ÷ Q
Average Variable Cost (AVC) = TVC ÷ Q
Marginal Cost (MC) = ΔTC ÷ ΔQ
Marginal cost is the additional cost of producing one more unit. AVC and MC tend to be U‑shaped due to initially increasing then diminishing marginal returns.
边际成本是多生产一单位产品所增加的成本。由于边际回报先递增后递减，AVC 和 MC 通常呈 U 形。
Total Revenue (TR) = Price (P) × Quantity (Q)
Average Revenue (AR) = TR ÷ Q = P
Marginal Revenue (MR) = ΔTR ÷ ΔQ
al cost. Normal profit is the minimum return needed to keep resources in their current use – y a normal profit. Supernormal (abnormal) profit is any profit above that level. The break‑even point occurs when TR = TC, i.e. AR = ATC.
利润是总收益与总成本之间的差额。正常利润是维持资源现有用途所需的最低回报——在经济术语中它是生产成本的一部分，因此零经济利润实际上表示正常利润。超常利润是高于该水平的任何利润。盈亏平衡点出现在 TR = TC，即 AR = ATC 时。
Profit = TR − TC
7. Profit Maximisation and Market Structures | 利润最大化与市场结构
In standard economic theory, firms are assumed to aim for profit maximisation. The optimal output occurs where the cost of producing an extra unit equals the extra revenue it brings in.
在标准经济理论中，企业被假定以利润最大化为目标。最优产量出现在额外生产一单位的成本等于其带来的额外收益之处。
Profit‑maximising condition: MC =
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